#nav{
    width: 1240px;
    text-align: center;
    margin: 0 auto;
}
#nav ul{
    height: 50px;
    width: 1240px;
    display:block;
    margin:0 auto;
}
#nav ul li{
    float: left;
    font-family: 微软雅黑;
    font-size: 14px;
    display: block;
    list-style: none;
    padding: 0 auto;
    height: 50px;
    line-height: 50px;
    text-align: center;
    width: 103px;
}
#nav ul li:hover a {
    color: black;
}
#nav ul li a{
    text-decoration:none;
    color: gray;
}